• Speech Sciences
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• v.11 no.1
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• pp.7-20
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• 2004

In this paper, we propose a two-step noise compensation algorithm in feature extraction for achieving robust speech recognition. The proposed method frees us from requiring a priori information on noisy environments and is simple to implement. First, in frequency domain, the Harmonics-based Spectral Subtraction (HSS) is applied so that it reduces the additive background noise and makes the shape of harmonics in speech spectrum more pronounced. We then apply a judiciously weighted variance Feature Vector Normalization (FVN) to compensate for both the channel distortion and additive noise. The weighted variance FVN compensates for the variance mismatch in both the speech and the non-speech regions respectively. Representative performance evaluation using Aurora 2 database shows that the proposed method yields 27.18% relative improvement in accuracy under a multi-noise training task and 57.94% relative improvement under a clean training task.

• The KSFM Journal of Fluid Machinery
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• v.2 no.3 s.4
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• pp.17-23
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• 1999

In the present numerical analysis, investigation of the effect of blade loadings from design shape on the slip factor variation was studied. Both the Eckardt radial bladed impeller and the backswept impeller were analyzed. In addition, a new design of the blade profile was arbitrarily attempted to generate a center-loading pattern in the original backswept impeller. Three dimensional compressible Navier-Stokes flow analysis with the Baldwin-Lomax turbulence model was applied to get the numerical slip factor at each impeller exit plane using the mass-averaging technique. The numerical slip (actors are in good agreement with the experimental ones and the Wiesner's slip factors deviate further from the numerical and experimental ones in both backswept impellers. Deviation angles and meridional channel loadings are found in no relation with the trend of change of the slip factor. Blade-to-blade loadings in midspan location are, however, found to have a direct relationship, especially at the sections where maximum loadings we to be expected. That information can be utilized in establishing an improved expression for slip factors in the future.

• Progress in Superconductivity and Cryogenics
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• v.5 no.3
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• pp.38-42
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• 2003

HTS transformer is promising one of HTS power applications to be commercialized in the near future. To realize the applications, insulation technology in the coolant, liquid nitrogen, should be established. So breakdown characteristics should be considered at insulation components; turn-to-turn, layer-to-layer, winding-to-winding, were investigated. Firstly breakdown strengths of Kapton films were compared with Kraft paper these are as turn insulator. And next the characteristics of surface flashover on FRP were measured and the influence on breakdown strength of bubble generated with joule heat was discussed with the shape of cooling channel between layers. Finally barrier effect at winding-to-winding was discussed.

• Journal of Biosystems Engineering
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• v.24 no.6
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• pp.493-500
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• 1999

In 1990's, two types of land consolidation has been widely carried out to enforce competativeness of rice production in Korea. One is so called large-scale land consolidation for resizing paddy field and farm road, the other is general land consolidation for changing both size and shape of field, water channel and farm road. This study was conducted to evaluate how much effect on fm mechanization the land consolidation had. To evaluate the influence of the land consolidation, theoretical analysis and surveys were accomplished. Land consolidation was analyzed to increase field efficiency by 180 to 670% depending on the type of land consolidation and machine selection. Also, land consolidation brought increment of real working time ratio by reducing traveling time on farm road. Trends of large scale mechanization and increment of custom work were observed to be accelerated by land consolidation. It also gave effect on the pattern of machine troubles. Farmers were conscious of the influence of land consolidation on machine utilization, however, in plains level of satisfaction was shown to be low.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.11
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• pp.831-837
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• 2003

This paper investigates the insertion loss of nosie barrier with a interference device, The efficiency of the conventional interference-type noise barrier depends on specific frequency, Thus this study is performed to improve the efficiency of the nosie barrierin the range of broadband frequency. by changing the shape of interference device and adding the channel with various depths, The boundary element method (BEM) is used to predict the insertion loss of noise barrier. Two-dimensional boundary element model is created to simulate the performance of long barrier with a line source.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.422-425
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• 2005

This study predicts the heat-affected zone (HAZ) after electrical discharge machining. To predict HAZ, the temperature distribution is calculated using FEM. Heat flux is calculated from electrical energy, and it can be assumed Gaussian distribution. Plasma channel expands as time goes. Copper and NAK80 are used as the workpiece material. The depth of HAZ in simulation is determined by temperature distribution. The simulation results were compared with a developed actual single discharge crater. Through investigating the cross section of simulated & actual craters, the depth of HAZ in simulation and experiment are compared. Simulation model can predict the crater shape.

• Transactions of Materials Processing
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• v.24 no.4
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• pp.248-255
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• 2015

The warm drawing of magnesium alloy AZ31B sheet is affected by temperature because tensile elongation is changed due to the elevated temperature. In the current study, the effect of temperature was investigated for an automotive dash panel part by both experimental and FE analysis. Tensile tests were performed to obtain mechanical properties for various temperatures. AZ31B alloy sheet shows increased total elongation with increasing deformation temperature in the range of 200 to 300℃. The heating channel inserted into the die was used to regulate and to obtain an optimal temperature. A temperature controller was constructed to reduce temperature variation. Warm drawing of magnesium alloy AZ31B was performed to produce the desired shape of the lightweight automotive dash panel. The simulated results showed good agreement with the experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.351-354
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• 2004

This work presents a simple and cost-effective approach for maskless fabrication of positive-tone silicon master for the replica molding of hyperfine elastomeric channel. Positive-tone silicon masters were fabricated by a maskless fabrication technique using the combination of nanoscratch by Nanoindenter ⓡ XP and XOH wet etching. Grooves were machined on a silicon surface coated with native oxide by ductile-regime nanoscratch, and they were etched in a 20 wt％ KOH solution. After the KOH etching process, positive-tone structures resulted because of the etch-mask effect of the amorphous oxide layer generated by nanoscratch. The size and shape of the positive-tone structures were controlled by varying the etching time (5, 15, 18, 20, 25, 30 min) and the normal loads (1, 5 mN) during nanoscratch. Moreover, the effects of the Berkovich tip alignment (0, 45$^{\circ}$) on the deformation behavior and etching characteristic of silicon material were investigated.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.7
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• pp.217-226
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• 2003

Twin screw extruders are the heart of the polymer processing industry. They are used at some stage in nearly all polymer processing operations. This paper is concerned with the basic elements of the extruder design. The proper design of the geometry of the extruder screw is of crucial importance to the proper functioning of the extruder. If the material transport instabilities occur as a result of improper screw geometry, even the most sophisticated computerized control system cannot solve the problem. For this purpose, a characteristic design on the screw flights shape of the closely intermeshing co-rotating twin screw extruder. This paper presents design parameters of double flighted screw and triple flighted screw elements, and characteristics of various screw channel area versus screw diameter ratio, K value, in the barrel of screw extruder.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.749-754
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• 2002

This paper investigates the insertion loss of nosie barrier with a interference device. The efficiency of the conventional interference-type noise barrier depends on specific frequency. Thus this study is performed to improve the efficiency of the nosie barrier in the range of broadband frequency, by changing the shape of interference device and adding the channel with various depths. The boundary element method (BEM) is used to predict the insertion loss of noise barrier. Two-dimensional boundary element model is created to simulate the performance of long barrier with a line source.